A winding mechanism of this type is described, for example, in Patent No CH 330202. This document discloses an alarm watch comprising a first energy accumulator formed by the barrel of the movement and a second energy accumulator formed by the barrel of the striking mechanism. The mechanism comprises a winding stem arranged to control all the operations of the movement and the alarm mechanism, and particularly the setting of the movement and of the striking mechanism, but also the winding of the movement barrel or of the striking mechanism barrel by rotating the winding stem in one direction or the other when it occupies its median winding position. To this end, the sliding pinion is meshed with the winding pinion via face gear teeth, and there is provided a crown wheel meshed with the winding pinion, and two intermediate crown wheels, both meshing with the crown wheel and intended to cooperate respectively with the ratchet of each of the barrels. The gearing of the intermediate crown wheels with the corresponding barrel ratchet is ensured by a spring that acts on the arbors of the intermediate crown wheels to push them into mesh with the corresponding ratchet. When the winding stem is rotated in one direction or in the other, by the tangential force exerted by the crown wheel on the intermediate wheels, one of the intermediate crown wheels winds the corresponding barrel whereas the other performs the unclicking operation. Unclicking entails a persistently weak, cyclical contact. Such a mechanism is fragile, owing to the permanent stress of the spring to ensure that the intermediate crown wheels mesh satisfactorily with the corresponding ratchet. Any loss in efficiency of the spring, due to fatigue or ageing, entails the risk that one or other of the intermediate wheels will no longer cooperate with the corresponding ratchet and the associated barrel will no longer be able to be wound. Another drawback is wear of the intermediate crown wheels during the unclicking operation. Moreover, this design requires checking the manufacturing tolerances of the spring.
Patent No CH 47977 also discloses a mechanism for winding and setting an alarm watch with two barrels. This mechanism comprises a winding ratchet for the movement barrel that is constantly engaged with a crown wheel meshing with a winding pinion and disposed to actuate the barrel arbor of the movement in only one direction of rotation of the stem. The winding ratchet of the movement barrel is used to transmit the reverse rotational movement of the stem, either to the winding ratchet of the alarm barrel, or to the alarm wheel, via an intermediate wheel pivoted on a lever operable from outside the watch. This mechanism has the drawback of requiring actuation of an external control member in addition to rotation of the winding stem in order to wind the striking barrel.